This invention relates to power supply technology, and more specifically, to an improvement in a power converter.
Solid state power converters are typically used on satellites, for example. Power converters of this kind, working in conjunction with solid state power amplifiers, need to meet aggressive system efficiency specifications. A typical source of input for these amplifiers and converters may be a high voltage bus from solar panels and batteries charged while the solar panels are energized. Since this source is limited, a high efficiency power converter having low losses is essential. In satellite applications, a 3% improvement over previous technology is an advantage.
In conventional power converters, the incoming voltage is pulse-width modulated to provide a predetermined constant voltage level at the output. The pulse-width modulator controller alternately turns on and off a switching device in accordance with the input voltage levels and the desired output voltage levels. By adjusting the duty cycle (Ton vs. Toff), the required output voltage level is attained. When the switching device is turned on, current passing through an inductor to the output creates an electromagnetic force on the inductor. When the switching device is turned off, the electromagnetic field collapses, inducing a flyback current that flows to the output through a commutating diode. The efficiency of this system may be increased by providing a more efficient mechanism than the lossy commutating diode which has a fixed voltage drop (e.g. 0.4 V for a Schottky diode). Synchronous rectifiers have been proposed as an alternative for the commutating diode, but specific synchronization systems that prevent conduction overlap between the switching devices are not available.
It is therefore an objective of this invention to provide a power supply that is very efficient, and that efficiently handles switching flyback or commutating currents. A further objective of this invention is to meet end-to-end efficiency specifications for solid state power amplifiers by increasing efficiency of the power converter. Yet another objective of the present invention is to prevent conduction overlap of switching devices, while controlling switching flyback or commutating current.